Digital circuitry has supplanted analog circuitry in many electronic systems, especially those used in data processing and telecommunications. Within such digital systems, there is often a need to process one or more analog signals, such as an analog video or voice signal, which may vary from 0 to V volts. To facilitate the processing by digital circuit elements within the electronic system, the analog signal is converted to a corresponding digital signal by an Analog-to-Digital (A/D) converter which serves to generate a digital word (i.e., a code) corresponding to the amplitude of the analog signal at a given instant. To more fully approximate the analog signal, the A/D converter samples the analog signal periodically. Such A/D converters are well known in the art.
The functionality of the A/D converter depends on its ability to generate all possible codes, (i.e., all 2.sup.n codes for an n-bit-wide A/D converter). In other words, the A/D converter should be capable of converting any analog voltage between 0 and V volts into the corresponding digital code. Failure of the A/D converter to convert a particular analog voltage to the corresponding digital code represents a fault (i.e., an error) which affects the A/D converter operation. To date, there has not been an efficient scheme for accomplishing built-in, self-testing of an A/D converter or a similar type of device to determine its ability to generate all possible codes.
Thus there is a need for a technique for accomplishing built-in self-testing of an A/D converter or the like to determine its ability to generate all possible digital codes.